The use of natural gas as an energy source in home and industry has won increasing importance recently. Besides transport of the gas from distant sources to consumers via pipelines, transport also is effected by sea after the gas has been liquified. The liquified gas then requires appropriate storage means when unloaded, whereby prescribed safety conditions must be met.
Thus the tank must be earthquake-proof on the one hand but must also be able to resist the strain of a gas cloud explosion.
Since such storage tanks are generally located near transportation routes, e.g. sea lanes, railway lines and highways, on which explosive substances are often transported, a gas cloud explosion in the area of the storage tank, e.g. in the event of an accident involving a vehicle loaded with fuel or the like, is always a possibility.
Storage tanks which meet these requirements consist of a steel-reinforced concrete exterior tank, in which is located a steel inner tank to hold the liquified gas, with appropriate insulation inserted between.
A familiar design provides that the structural connection between the tank wall and the base, which is necessary to transfer the horizontal load applied to the steel-reinforced concrete tank, e.g. in the case of an earthquake or a gas cloud explosion, is a monolithic rigid angle.
However, this design has the disadvantage that temperature loading conditions, particularly when they arise suddenly, as when the inside of the steel-reinforced concrete tank is dampened by liquified natural gas, can hinder deformation of the tank wall and thus lead to bending stress on the tank wall and the tank base. Such temperature loading conditions must be reckoned with, for leaks or splashing over of the contents of the inner tank, which is usually open at the top, can bring the liquified gas into contact with the steel-reinforced concrete inner wall, so that the connection between wall and base of the steel-reinforced concrete tank is greatly endangered, and this danger can lead to permanent damage.
Another steel-reinforced concrete tank design also is known, in which the tank wall is a separate unit located on the base. A construction of this type does not, however, fulfill the safety requirements in the case of a gas cloud explosion, since the tank wall could then be shifted as a whole on the base.
The object of the invention is to create a tank with steel-reinforced concrete exterior of the last-named type, which fulfills safety requirements as well as avoiding uncontrollable bending moment stresses under temperature loading conditions, independent of their intensity, which can only be roughly estimated, and thus leads to a decisive increase in the operating safety of the tank.